Silicon carbide (SiC) is wide band gap semiconductor (EG=3.0 eV) for high-temperature, high-power and radiation hardened electronic devices. SiC can be thermally oxidized to form SiO2, and the SiC/SiO2 interface can be used to produce devices, such as transistors, charge-coupled devices and non-volatile memories. However, the inversion layer mobility on SiC can be low, limiting the switch-on resistance (Rdson). Further, the gate oxide in SiC is highly susceptible to dielectric breakdown due to the high electric fields in SiC.
Circuits in which a SiC device is connected in series with a silicon MOSFET are known. An example is disclosed in U.S. Pat. No. 6,373,318 to Dohnke et al. issued Apr. 16, 2002. However, the circuit of Dohnke et al. has a grid-cathode voltage of the junction field effect transistor (JFET) at a voltage less than the source voltage of the metal oxide semiconductor field effect transistor (MOSFET).
The gate drain junction of the SiC JFET of Dohnke et al. supports the high voltage. Thus, connecting the junction on the gate side and leading up the gate driver can lead to avalanche current flowing into the gate circuit when the device is in the blocking mode.
Although it has been suggested to try using an SiC device with a silicon MOSFET, practical devices are limited by packaging and thermal management consideration.